Saute onions in melted butter in a large soup pot for 15-20 minutes or until onions begin to turn brown and transparent Add broth, salt and garlic powder and bring to boil. Reduce heat and simmer at least one hour. Add grated parm cheese during the last ten minutes. When ready to serve, preheat oven to 350 and brown bread for 10 minutes. Then set oven to broil. Put soup in individual oven safe bowls. Put bread in so that the top sticks above the soup. Add slice of Swiss and Mozzarella on top of the bread and sprinkle with the parm cheese. Put soup bowls on baking sheet and broil for 5 to 8 minutes until cheese is brown. Per Serving (excluding unknown items): 1026 Calories; 70g Fat (61.3% calories from fat); 71g Protein; 28g Carbohydrate; 2g Dietary Fiber; 232mg Cholesterol; 2524mg Sodium. Exchanges: 1 Grain(Starch); 9 Lean Meat; 1 Vegetable; 9 Fat.